Research On Packet Scheduling Algorithms Of Wimax System

In the recent years, wireless broadband technologies have made great progress. On behalf of new broadband wireless acess technology, WiMAX bring new energy to broadband wireless markets. The develepment of WiMAX goes through fixed, portable and mobile three phases, which caters to the trend of Internet and peoples'consuming habits, and provides convenient and timing access to mobile users.Therefore WiMAX will be more important in the future.WiMAX supllies connection-oriented services and supports various multimedia services. Different services have different quality of service. In order to meet the Qos of different service flow and ensures efficient transmisson and effective bandwidth utilization, we need to design a good packet scheduling algorithm. Research on advanced packet scheduling algorithms is the key to improving system throughput, guaanteeing the fairness among users and satisfying the Qos of services.Nowadays there have been many mature packet scheduling algorithms, but little can adapt to WiMAX system. On the basis of previous working, this passage illustrates a hierarcical packet scheduling method for WiMAX. The first stage happens among different services. In this paper, we adopt an algorithm called DPFQ which has higher fairness. The second stage happens among the different connections in the same service. Considering the requirements of all connections, different scheduling strategies are applied to different services. As there may be network conjestion, we add an acess control algorithm to original sceduling structure. Simultaneously,in order to increase the fairness,this paper improves the first scheduling stage by applying a new parameter updating rule.Finally, by the simulation of NS2, the results show the algorithm this passage proposes improve many performances.